Engine
Engine 27HP — Westerbeke 30B Three wiring diagram
Westerbeke 30B Three: 27 hp at 3600 rpm, 1.2 kW starter and 50 A alternator. Manual cold-cranking reference is 190 A at 10 V; 280 A surge remains a planning estimate. Separate 20 A harness breaker protects the controls and fuel-pump circuit.
- Continuous draw
- 190 A
- Rated output
- 50 A
- Surge current
- 280 A
Wiring diagram
How the 30B Three 27HP is wired.
Open this example in Crimp to use your own parts and cable lengths. Review the assumptions and installation notes as you adapt the circuit.
Cable sizing for this example
Use the diagram as a starting point for your installation. Replace the example equipment and cable lengths with your own, and check the connections against your exact model's instructions.
3 m one way
12 V system
- Wire
- 120 mm² · 4/0 AWG
- Example fuse
- 250 A
- Cranking current
- 190 A
- Voltage drop
- 1.4%
Sized against ABYC E-11. The cranking current is what the starter draws. ABYC E-11 doesn't require a fuse on a cranking-motor conductor, so the fuse shown is the usual cranking-rated (Class T) choice, sized to hold the crank without nuisance tripping — it isn't there to protect the wire. The length is one way; voltage drop includes an equal-length return.
Run-length and manufacturer assumptions
The editable example uses 3.048 m (10 ft) runs unless a shorter run is stated. Metric overviews round these to 3 m. Adapt the parts and lengths to your installation before choosing cable and protection.
Supporting parts
- 6.1 m total of 120 mm² (4/0 AWG) marine cable
- Terminations for 120 mm² cable, matched to the equipment's screw terminals, leads or studs
- 250 A cranking-rated (Class T) fuse at the battery
- Heat-shrink, strain relief and terminal boots sized to the cable
Check stud sizes, fuse type, run length and how warm the space gets against the gear you actually have before you order.
Installation notes
Before you install.
Open a question for model-specific guidance and sources.
Verified against the manufacturer's documentation (rev. Publication 36906 \u2014 revision five, January 2011), checked 2026-10-01. Manufacturer documentation →
Engine and edition
Use the 30B Three column, not the 20B Two or 30C Three. Westerbeke specifies 27 hp at 3600 rpm, a 12 V negative-ground starting system, 1.2 kW reduction starter and 50 A alternator. The battery recommendation is 600–800 CCA. Optional or replacement charging equipment must be identified from its own label.
What the terminals mean
`Starter` represents the high-current starter supply, `Alt B+` the alternator charging output, and `Block GND` the intended negative return on an earth-return installation. They are functional drawing ports, not three interchangeable physical studs. Trace any factory link between alternator B+ and the starter battery stud before changing it; do not duplicate or remove that link without accounting for the original harness.
Controls and protection
On the Captain and Admiral panels, PREHEAT powers the glow plugs, alternator excitation, fuel lift pump and fuel solenoid, and enables START. START will not operate unless PREHEAT is held. The engine-mounted 20 A manual-reset breaker protects the DC harness and panel circuit; a trip removes fuel-pump power and can stop the engine. Find and repair the fault before resetting.
Checks and model limits
The specification sheet provides an actual cold-cranking reference of 190 A at 10 V and its stated minimum speed. The catalog now uses 190 A for the starting load, but this is a test condition rather than a guaranteed maximum. Its 280 A surge remains an estimate. The alarm system distinguishes low-oil-pressure and high-temperature warnings; connect the supplied alarm buzzer so it can be heard. The drawing does not simulate preheat, fuel-pump consumption, alarm thresholds or shutdown behavior.
Source: manufacturer document — panel instructions printed pp. 6–7 (PDF 12–13), breaker/alarms p. 11 (PDF 17), 30B/C specifications p. 56 (PDF 64). Legacy copies hosted outside the manufacturer site are manufacturer-authored archive documents; the review date does not make them current installation instructions.
Fit check
Connect it to the rest of your system.
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The model only picks parts and draws the connections. Every wire size and fuse rating still comes from Crimp's own sizing, never from the model.
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Technical reference
Specifications and terminal map.
Check the model, ratings and connection points against your own unit before choosing installation hardware.
Catalog specification
Westerbeke 30B Three: 27 hp at 3600 rpm, 1.2 kW starter and 50 A alternator. Manual cold-cranking reference is 190 A at 10 V; 280 A surge remains a planning estimate. Separate 20 A harness breaker protects the controls and fuel-pump circuit.
- Continuous draw
- 190 A
- Rated output
- 50 A
- Surge current
- 280 A
Terminal map
Catalog connection points, current direction and planning limits. Check the manufacturer's pinout and connector ratings before installation.
Starter
positive · input
Alt B+
positive · output
Block GND
ground · bidi
Sources and sizing method
Equipment specifications. Model details, ratings and terminal roles come from the catalog. Check your unit’s label and current manufacturer documentation for its exact revision.
Example sizing. Sized against ABYC E-11. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. Results use the example current and run length shown above. Set your actual equipment, lengths and installation conditions in Crimp before choosing hardware.
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Plan your installation with 30B Three 27HP.
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